1. Field of the Invention
The instant invention relates to a cutting tool comprising at least one exchangeable cutting blade mounted on a parallelepiped cutting blade holder which is adapted to be fixed at a tool body by a setscrew passing through the cutting blade holder such that the holder is pressed flat against a first recess surface and, at the same time, in the direction of a second recess surface extending at an angle with respect to the first one, the setscrew penetrating the cutting blade holder with clearance for freely adjustable fastening such that it includes an angle of substantially the same size with both recess surfaces and presses the cutting blade holder against the second recess surface by two adjustable support members of which at least one is designed as a rotatable eccentric supporting pin the axis of which extends substantially parallel to the associated second recess surface and which is supported in a fitting recess of the cutting blade holder or of the tool body.
2. Discussion of the Background
DE-OS 25 05 515 discloses a cutting tool which comprises at least one exchangeable cutting blade which is attached to a prismatic cutting blade holder received in a corresponding recess formed in the tool body. The cutting blade holder itself is adapted to be fastened at the tool body by a setscrew which penetrates the cutting blade holder such that the holder is pressed flat against a first recess surface and, at the same time, in the direction of a second recess surface which extends at an angle with respect to the first one.
The cutting blade holder is fixed by means of a central setscrew and the fixing in position is obtained by means of edge surfaces of the cutting blade itself which can be moved into abutting contact with supporting surfaces of the cutting blade holder. The setscrew thus presses the cutting blade holder against a first recess surface in such manner that, at the same time, the cutting blade can be centered at the supporting surfaces. In the final analysis this has the consequence that adjustment of the cutting blade holder is no longer possible with this cutting tool because the setting up and orientation of the cutting blade are determined by the configuration of the recesses and supporting or bearing surfaces of the tool body.
There is a general need for more varied or universal application of the tool body and cutting plate holders in view of the fact that any cutting tools fitted with cutting blades or small cutting plates are very expensive. In the course of this development a universal tool body came to be fitted with adjustable cutting blade holders, so-called interchangeable or insert blade cassettes, thus providing a subassembly which permits a variety of special machining processes to be carried out in a single working pass by selectively combining the individual cassettes. Such a tool subassembly is described, for example, in the journal "tz fur Metallverarbeitung", vol. 12/81. In the case of the aggregate known from this journal the cutting blade holders are received so as to be adjustable in axial fitting bores, each cutting blade holder in turn carrying a radially displaceable blade or tip carrier.
With modern special tools which are intended to produce a number of closely tolerated functional surfaces in a single operating step which surfaces, moreover, must be in closely tolerated relative positional arrangement, however, it was found that it is not sufficient to adjust the cutting blade in axial and radial directions each with a translatory direction of movement. Rather, it proved to be desirable to provide the possibility of tilting adjustment of the cutting blade and thus of the interchangeable blade cassette so that the setting angle or blade angle with respect to the direction of advance can be fixed accurately. It is the task of the manufacturer of such special tools to provide the user with a tool in which the individual cutting blade holders already are aligned accurately with respect to each other so that all the user has to do is to clamp the tool in the respective machine tool.
The adjustment of such special tools usually requires high precision optical means so that the adjusting procedure becomes rather expensive. For this reason the fastening of the holders of the cutting blades or plates at the tool body must be so secure that the cutting blade holders cannot become misaligned during shipment or use of the special tool. Yet on the other hand there is the demand that the adjustment of the cutting blade holder be realizable by very simple manipulations so that the adjusting can be carried out in little time.
DE-OS 33 27 478 describes a cutting tool with which additional safety measures can be dispensed with, such as the provision of seals on fastening means for the interchangeable blade cassettes to eliminate undesired adjustments. With this cutting tool the exchangeable cutting blade is mounted on a prismatic cutting blade holder which is adapted to be fixed at the tool body by a setscrew passing through the cutting blade holder such that the holder is pressed flat against a first recess surface and, at the same time, in the direction of a second recess surface extending at an angle with respect to the first one. The setscrew penetrates the cutting blade holder for freely adjustable fastening with clearance such that it includes an angle of substantially the same size with both recess surfaces and presses the cutting blade holder against the second recess surface by way of two adjustable support members. The adjustable support members are embodied by supporting screws which act through cutting blade holders such that the tip of the screw which is to effect the support projects substantially vertically above the surface of the cutting blade holder facing the second recess surface. FIGS. 1 and 2 which will be described in greater detail below show such a cutting tool.
This known cutting tool proved rather successful in practical application because simple manipulations assure that the cutting blade holder is fixed at the tool body in a statically defined manner and without becoming loose. The clearance between the setscrew and the corresponding recess provided in the cutting blade holder readily may be kept so large that the necessary translatory and rotational adjustment degrees of freedom are made available which are within very close limits. The stability of the cutting blade holder is not impaired by the bore receiving the setscrew. This is all the more so as the flat surface contact into which the cutting blade holder is pressed provides an effect which increases the stability and creates good conditions for having the main cutting forces accommodated with the least possible loading of the cutting blade holder.
Such a cutting tool is rather expensive because of the accuracy required in adjustment and fitting. For this reason it can be used especially economically only if the tool body is furnished with a plurality of such cutting blade holders. In this event the tool may be applied so as to produce numerous functional surfaces having a predetermined and very closely tolerated positional association in just one pass. This requires the individual cutting blade holders to be fixed at the tool body staggered radially and/or axially and/or in circumferential direction in the most limited space. The cutting tool according to DE-OS 33 27 478 was of such structure that, while the supporting screws were freely accessible, the cutting blade holders not always could be mounted in a sufficiently small space. Often excessive displacements of the individual cutting blade holders had to be put up with in order to guarantee the accessibility of the fastening screws and supporting screws of each individual cutting blade holder. That led to an increase of the masses being moved and this could influence the dynamic cutting behavior of the cutting tool.
A cutting tool in accordance with the present invention is suggested in an earlier patent application P 35 02 346.5-14 in order to house a plurality of cutting blade holders, freely adjustable, in the most limited space. This proposal makes it possible to mount even two cutting blade holders, for instance in a shaft tool designed as a boring or milling tool in the same axial plane directly adjacent each other and yet assure free accessibility of the supporting members. It was found that the small cutting plates or cutting blades even can be positioned directly adjacent each other without any axial offset provided a countersunk head rest surface is designed suitably for the setscrew passing through the cutting blade holder. Much greater flexibility as to the composition or staggering of the cutting blades and/or cutting blade holders at the cutting tool was provided by this proposal.
Furthermore, an especially advantageous modification of this improved cutting tool is given if the supporting eccentric pin is received rotatably in a fitting recess of the cutting blade holder or of the tool holder. This earlier application suggests several possibilities of how to retain the eccentric pin in a close-tolerance recess. However, a feature which all of these solutions have in common is that they render the manufacture of the cutting blade holder or of the cutting tool more expensive to a greater or lesser extent. It is, therefore, an object of the instant invention to provide a cutting tool of the kind recited initially with which the fastening of the eccentric pins has only minimum effect on the costs. It is another object of the invention to provide a cutting tool of the kind specified which continues to safeguard that the eccentric pins are perfectly securely fixed in position.
These and other objects which will become apparent as the specification proceeds are met in that the supporting eccentric pin is held in the fitting recess by a hairpin-type spring.